Geralf's Mindcrusher

Self-mill decks have always wanted a body that fills the graveyard twice for the same investment, and undying is the elegant way to get it. A 5/5 that mills five on arrival is fine value once; the recursion is what turns it into an engine. When it dies without a counter, it returns and mills five again, two enter-the-battlefield triggers off one card, separated only by a trip through combat or a sacrifice outlet, in any deck that treats its own library as a resource pool. The mill clause naming "target player" cuts both ways, which is the small lever that keeps it from being a purely self-fueling tool: aim it across the table when a mill plan calls for it. The undying return grows the body, which is also the natural off-switch, since the returned creature comes back with a counter and will not return again unless that counter is removed. That same counter is what aristocrat-style builds want to strip off: blink the creature, bounce it, or remove the counter and the whole cycle resets. The 5/5 frame matters too, because the recursion is not free filler in the sky but a clock that pressures the opponent while it digs. It is a graveyard-matters payoff and a beater folded into one expensive package, the kind of card that earns its slot in decks that win by mining through themselves rather than racing past their opponent.